News

Vierendeel bridge faces demolition in Belgium

Saturday, August 29, 2009

I usually don't pay much attention to bridges outside of the U.S., as I have my hands full just keeping up with this country. However, the Flemish Association for Industrial Archaeology sent a note about the upcoming replacement of a very rare bridge in Belgium. The Scheepsdale Bridge in the town of Brugge features a Vierendeel truss with a swing span.

Belgian engineer Arthur Vierendeel (1852-1940) developed the unusual design, consisting of a truss with no diagonal members. To compensate for the lack of diagonals, the design incorporates rounded corners to handle bending forces. While several Vierendeel trusses remain in Belgium, the Scheepsdale Bridge is reportedly the last example with a movable span.

The U.S. only has a handful of Vierendeel truss bridges, all built over the Verdugo Wash in Los Angeles. However, Vierendeel trusses (or a variation) have been used to provide bracing for other bridges, including the towers of suspension bridges. It could be argued that the towers of the Golden Gate are Vierendeels, oriented vertically. The concept was also used in the construction of the walls of the World Trade Center.

At any rate, the Flemish Association for Industrial Archaeology is campaigning to save all or part of the Scheepsdale Bridge. They write:

Please help us and send a letter or a e-mail which pleads for saving at least a relevant part of this bridge to:

Comments (1)

A message I sent to David Yoemans, Stephen Kelly and Patrick Sparks - all members of The International Scientific Committee on the Analysis and Restoration of Structures of Architectural Heritage (ISCARSAH) founded by ICOMOS in 1996 as a forum and network for engineers involved in the restoration and care of building heritage. The first meeting of the ISCARSAH took place at the Engineering University in Rome in March of 1997 and the committee has met twice a year since then in venues all over the world.

Members of the ISCARSAH are composed of internationally renowned engineers, scientists, architects, specialists, and educators with representation from Europe, Asia, Australia, North and South America.

Dear David/Stephen/Patrick,

I sent the following to officials in Bruuge last month. The US has few examples of Vierendeel trusses, aside from three bridges in Glendale, CA, a suburb of LA, though the Golden Gate and Triborough bridge towers are impressive (renamed John F. Kennedy Bridge in 2008). Robert Moses employed the services of famed bridge designer Othmar Ammann. At that time, Ammann had held the position of chief engineer at the Port of New York Authority for seven years. The towers reflected newer design and construction conventions than those originally proposed by Arthur I. Perry. Perry’s original plans for the Triborough towers recalled the dual-arched Gothic design of the Brooklyn Bridge.

Simple geometry and uncluttered lines characterized Ammann's new design. The towers, as with the ornamental light posts on the bridge, reflect the Art Deco skyscraper aesthetics of the era. NY City’s write-up does not reference Vierendeel as the influence for the towers, but Ammann certainly would have known about the structural form.

Though Joseph Strauss is attributed as the engineer-of-record of the Golden Gate, senior engineer Charles Alton Ellis, collaborating with famed bridge designer Leon Moisseiff, was the principal engineer. Moisseiff produced the basic structural design. The literature on Golden Gate doesn’t reference Vierendeel either.

A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring at or near to its center, about which the turning span can then pivot horizontally. The primary disadvantage is that the central pier forms a hazard to navigation thus reducing the width of the channel. Asymmetrical bridges may place the pivot near one side of the channel.

The other interesting feature of a swing bridge is that when open, the bridge will have to maintain its own weight as a balanced double cantilever, while when closed and in use for traffic the live loads will be distributed as in a pair of conventional truss bridges, which may require additional stiffness in some members whose loading will be alternately in compression or tension.

In summary, Vierendeel trusses are rare examples. Scheepsdale (1933), being the last documented of this bridge type to its designer, a native Belgian, merits protection, http://bridgehunter.com/ (Scroll down on Bridge Hunter’s web site to find mention of Sheepsdale.) http://users.telenet.be/karel.roose/vierendeel/vierendeel.ht... The Flemish have done a thorough job researching, writing up and placing Scheepsdale Bridge into a global context.

I urge the officials responsible in Bruuge, a World Heritage city, to reconsider replacing the Scheepsdale Bridge.

I can attest that America has only three Vierendeel trusses in Glendale, near Los Angeles (Geneva Street (1938), Glenoaks Blvd. (1938), Kenilworth Avenue (1936), all over Verdugo Wash.

The Golden Gate and Triborough bridges have suspension towers based on Vierendeel’s principal of no diagonal chords, only rectangular.

Arthur Vierendeel is Belgian. To take out the last Vierendeel truss attributed to the originating engineer, would be unfortunate. The Scheepsdale Bridge, in addition to the Flemish Association for Industrial Archaeology (VVIA), is also highlighted on the World Heritage alert.

Eric DeLony

Chief (Emeritus), Historic American Engineering Record, National Park Service

HAER is a federal program, established in1969, to create a national archive of America's engineering, industrial and technological heritage. HAER documentation has multifold purposes: it provides a permanent record of America’s engineering, industrial and technological heritage; it serves as a model to document large-scale engineering and industrial works; it enables the public to understand and interpret often complex industrial processes and engineering works; and, through its summer surveys, provides an educational opportunity to student architects, landscape architects, engineers, and historians.